The present applicant previously proposed a process for producing a high-purity chlorophosphite in which phosphorus trichloride and a phosphorous acid triester are allowed to react in the presence of a catalyst to produce a chlorophosphite, and a reaction liquid containing the chlorophosphite produced is separated from the catalyst in a short time (see Patent Document 1). An advantage of the process is to provide a high-purity chlorophosphite in a high yield. Another advantage of the process is that the process is capable of selectively producing a chlorophosphite and a dichlorophosphite.
In the production process described above, a reaction liquid containing a chlorophosphite is supplied to a heated inner surface of an evaporator, and is allowed to flow down in a filmy state along the inner surface to cause rapid vaporization and to cause the chlorophosphite as a target substance to evaporate and be separated from a catalyst. In this case, depending on the kind of the catalyst, the solidified catalyst is adhered in a powdery state on the inner surface of the evaporator, causing trouble in continuous production in some cases. The phenomenon also causes a decrease in the yield of the target chlorophosphite.
Further, the present applicant previously proposed the use of a quaternary phosphonium salt as a catalyst usable in the production process described above (see Patent Document 2). However, the case where this compound is used as a catalyst also causes trouble as described above in some cases.
Patent Document 1: Japanese Patent Laid-Open No. 61-112088
Patent Document 2: Japanese Patent Laid-Open No. 2-145594